One known rotation transmission devices used to selectively transmit rotation from a driving shaft to a driven shaft includes a two-way clutch, and an electromagnetic clutch configured to selectively engage and disengage the two-way clutch.
For example, in JP Patent Publication 2012- 149746 A, a rotation transmission device is disclosed which includes a two-way clutch, and an electromagnetic clutch configured to selectively engage and disengage the two-way clutch. The two-way clutch includes an outer ring, an inner ring mounted inside the outer ring, and a control retainer and a rotary retainer mounted between the outer ring and the inner ring, with the bars of one retainer arranged circumferentially alternating with the bars of the other retainer. The two-way clutch further includes opposed pairs of rollers, each pair being received in a pocket defined between each adjacent pair of bars, and elastic members each disposed between each opposed pair of the rollers to bias the opposed pair of rollers away from each other into stand-by positions where the respective rollers can instantly engage a cylindrical surface formed on the inner periphery of the outer ring and cam surfaces formed on the outer periphery of the inner ring, whereby when the inner ring rotates in one direction, one of each opposed pair of rollers engages the cylindrical surface and the cam surface, thus transmitting the rotation of the inner ring to the outer ring.
The electromagnetic clutch, which is used to control the two-way clutch, is configured such that when the electromagnet is energized, the control retainer is moved in the axial direction, and simultaneously, the control retainer and the rotary retainer are rotated in the direction in which the circumferential widths of the pockets decreases by the action of a torque cam, as a motion converter mechanism, provided between the opposed surfaces of the flanges of the control retainer and the rotary retainer, thereby moving the pairs of rollers through the bars of the respective retainers to the disengaged positions and preventing transmission of rotation from the inner ring to the outer ring.
In this rotation transmission device, when the electromagnet of the electromagnetic clutch is de-energized, the control retainer and the rotary retainer are rotated relative to each other in the direction in which the circumferential widths of the pockets increase under the biasing force of elastic members disposed between the respective opposed pairs of rollers, so that the opposed pairs of rollers instantly engage the cylindrical surface and the cam surfaces. This rotation transmission device is therefore extremely small in play in the rotational direction and thus fast in response.